IAGA/ URSI Joint Working Group on
VLF/ELF Remote Sensing of Ionospheres and
Magnetospheres Newsletter
Editor: Craig J. Rodger
No. 28,
December 2013
Dear Colleagues,
This is my last VERSIM newsletter as editor, and the 11th news
letter I have helped prepare. As many of you will know, I stood
down from the role as IAGA co-chair at the 12th IAGA
Scientific Assembly in Mérida, Mexico (26 - 31 August 2013),
having accepted the role at the 23rd IUGG General Assembly in
Sapporo in 2003. I am delighted that Jacob Bortnik (UCLA,
USA) accepted the nomination to replace me, and was elected
by unanimous vote at our Business Meeting in Mérida. To aide
the transition I offered to produce this years newsletter,
although I expect this to be my last. But I step down happy, as
the community is strong, as emphasised by this newsletter!
Dear friends and colleagues,
However, I hope you will still see my research work, and hear
from me at VERSIM meetings and sessions. I am not retiring or
leaving science (I'm only 41!). However, I feel that after more
than a decade severing as VERSIM chairman it would be good
for the community for someone else to take up the role.
Let me firstly convey my deep gratitude for being elected to
the leadership of the VERSIM group. I am humbled to cochair a group which was home to some of the true pioneers of
radio science (and space science in general) and continues to
be central, relevant, and integral to a host of related
disciplines.
This year the VERSIM community formally met at our business
meeting in Mexico, while next year we will have two formal
gatherings. As I hope you remember, the 6th VERSIM
workshop is about a month away, 20-23 January 2014 at the
University of Otago, in Dunedin (New Zealand). Then later in
the year, we will gather in August at the 31st General Assembly
and Scientific Symposium in Beijing from 16 - 23 August 2014.
I am excited to see what developments take place in our field
during my tenure, at a time when our planet’s surface and the
geospace environment is instrumented at unprecedented
levels, storage and computation is cheap and powerful, and a
plethora of techniques and algorithms is becoming available
to extract insights that simply could not be gleaned otherwise.
Thankyou to all of you for supporting the VERSIM community
in the time I have acted as chair – I would ask you to continue
your scientific activities and support Jacob in his new role.
Submit material to our newsletters, come to our business
meetings, and most importantly work together to do interesting
and stronger science. Finally, I hope to see many of you in New
Zealand. I wish you a successful 2014!
How could I not be excited? I expect VERSIM to lead in this
effort, and it is my pleasure and honor to be a part of it.
Jacob Bortnik
IAGA co-chair VERSIM working group
Upcoming meetings
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Craig J. Rodger
outgoing IAGA co-chair VERSIM working group
1
6th VERSIM Workshop, Dunedin, New Zealand from 20 - 23
January 2014.
2014 Geospace Environment Modeling (GEM) Summer
Workshop, Portsmouth, USA from 15 - 20 June 2014.
40th COSPAR Scientific Assembly, Moscow, Russia from 2 10 August 2014.
31st General Assembly and Scientific Symposium of URSI,
Beijing, China CIE from 16 - 23 August 2014.
AGU Chapman Conference on Low Frequency Waves in Space
Plasmas, Jeju Island, Republic of Korea from 31 August - 5
September 2014.
Geospace Revisited Conference, Rhodes, Greece from 15-20
September 2014.
2014 Fall Meeting of the American Geophysical Union, San
Francisco, USA from 15 - 19 December 2014.
Reports from VERSIM research groups 2013
This based on information received by the outgoing IAGA cochairman, Craig Rodger, by email from the VERSIM
membership. Some reports have been slightly edited so the
newsletter has consistent formatting. Hopefully this has not
introduced any significant typos.
Belgium - Belgian Institute for Space Aeronomy (IASBBIRA), Belgium, report by Fabien Darrouzet, Sylvain Ranvier,
Herve Lamy, Johan De Keyser.
We continue our project to detect whistlers with VLF
measurements. A VLF antenna has been installed in October
2010 in Humain, Belgium (Lat. ~50.11°N, Long. ~5.15°E), in
order to detect whistlers and determine electron densities along
propagation paths. The VLF antenna is made of two
perpendicular magnetic loops, oriented N-S and E-W and with
an area of approximately 50 m2 each. The antenna is fully
working since August 2011.
This antenna is part of AWDAnet, the Automatic Whistler
Detector and Analyzer system's network. This network covers
low, mid and high magnetic latitudes including conjugate
locations. It has been initiated by Dr. J. Lichtenberger
(Hungary). Worldwide; currently, 23 antennas are in operation
and 21 are planned/in construction.
We have started some comparisons with density data
measured by the WHISPER instrument onboard the 4 Cluster
satellites. First results are promising, but a comprehensive study
needs more investigation.
Statistical analysis and first comparisons with models and
satellite data have been presented at the EGU General
Assembly (Vienna, Austria) in April 2013 and at the IAGA
Conference (Merida, Mexico) in August 2013.
We have started a study of feasibility to install another
antenna at the Belgian Antarctic station (Lat. ~71.57°S, Long.
~23.20°E). This antenna would be composed by two search
coils, without a mast in order to support the weather at such
latitudes.
Czech Republic - Report by Ondrej Santolik, representing the
Institute of Atmospheric Physics ASCR and Charles University.
We analyzed VLF electromagnetic waves with periodic time
modulation of wave intensity, so-called quasi-periodic (QP)
emissions. A systematic study based on the measurements of
the low-altitude DEMETER spacecraft [1] inspired us to
perform a case study of a QP event observed simultaneously on
board the DEMETER and Cluster spacecraft allowed us to
estimate the spatial and the temporal extent of the emissions [2].
The analyzed QP event lasted as long as 5 hours and it spanned
over the L-shells from about 1.5 to 5.5. Curiously, the same QP
modulation of the wave intensity was observed at the same time
at very different locations in the inner magnetosphere. ULF
magnetic field pulsations with a period roughly comparable to
the period of the QP modulation were detected by the fluxgate
magnetometers on board Cluster near the equatorial region,
suggesting that these are likely to be related to the QP
generation.
Encouraged by these results, we conducted a systematic
survey of QP emissions observed by the Cluster spacecraft
during the first 10 years of operation (2001-2010) [3]. A
detailed wave analysis reveals that the wave vectors of the
emissions are nearly field-aligned in the equatorial region, but
they become oblique at larger geomagnetic latitudes. This
2
suggests that the waves propagate unducted. ULF magnetic
field pulsations were detected at the same time as QP emissions
in 4 out of the 21 analyzed events. They were polarized in the
plane perpendicular to the ambient magnetic field, and their
frequencies roughly corresponded to the modulation period of
the QP events.
We have also used VLF electromagnetic wave data
measured by DEMETER (Detection of Electro-Magnetic
Emissions Transmitted from Earthquake Regions) to check for
the presence of statistically significant changes of natural wave
intensity (due to signals from lightning) related to preseismic
activity [4]. All the relevant data acquired by DEMETER
during almost 6.5 years of the mission have been analyzed
using a robust two-step data-processing schema. This enabled
us to compare data from the vicinity of about 8400 earthquakes
with an unperturbed background distribution based on data
collected during the whole DEMETER mission and to evaluate
the statistical significance of the observed effects. We were
finally able to confirm previously reported results of a very
small but statistically significant decrease of the wave intensity
(by 2 dB) at frequencies of about 1.7 kHz. The effect is
observed for a few hours before the times of the main shocks
and occurs only during the local night.
We have installed and operated new ground-based
broadband measurements ELF to HF) related to lightning
research in collaboration with Laboratoire Souterrain a BasBruit, Rustrel, France. The thunderstorm activity is
continuously monitored in a favorable electromagnetic
environment on the summit of La Grande Montagne (1028 m,
43.9410ºN, 5.4836ºE), Plateau d'Albion. These measurements
are prepared as a ground-based counterpart of instrumentation
which is being developed for spacecraft measurements in the
frame of TARANIS and Resonance projects. Results from the
previous campaign in Prague [5] demonstrate promising
possibilities of these new broadband measurements.
References:
[1] Hayosh, M., D. L. Pasmanik, A. G. Demekhov, O. Santolik, M. Parrot, and
E. E. Titova (2013), Simultaneous observations of quasi-periodic ELF/VLF
wave emissions and electron precipitation by DEMETER satellite: A case
study, J. Geophys. Res. Space Physics, 118, doi:10.1002/jgra.50179
[2] Nemec, F., O. Santolik, M. Parrot, J. S. Pickett, M. Hayosh, N. CornilleauWehrlin, Conjugate Observations of Quasi-Periodic Emissions by Cluster and
DEMETER
Spacecraft,
J.
Geophys.
Res.,
118,
198-208,
doi:10.1029/2012JA018380, 2013.
[3] Nemec, F., O. Santolik, J. S. Pickett, M. Parrot, N. Cornilleau-Wehrlin,
Quasiperiodic Emissions Observed by the Cluster Spacecraft and Their
Association with ULF Magnetic Pulsations, J. Geophys. Res., 118, 4210-4220,
doi: 10.1002/jgra.50406, 2013.
[4] Písa, D., F. Nemec, O. Santolík, M. Parrot, and M. Rycroft (2013),
Additional attenuation of natural VLF electro- magnetic waves observed by the
DEMETER spacecraft resulting from preseismic activity, J. Geophys. Res.
Space Physics, 118, 5286–5295, doi:10.1002/jgra.50469.
[5] Kolmasova, I., and O. Santolik (2013), Properties of unipolar magnetic
field pulse trains generated by lightning discharges, Geophys. Res. Lett. 40,
doi:10.1002/grl.50366.
Fiji - The University of the South Pacific, Suva, Fiji, report
from Sushil Kumar.
We continue participating in the World Wide Lightning
Location Network (WWLLN) since our joining in 2003. Using
the WWLLN setup we are recording the narrowband data on
six transmitter signals using SoftPAL data acquisition system.
The analysis of short-timescale (∼1–100 s) perturbations (early
VLF events) on four Very Low Frequency (VLF) transmitter
signals (NWC, NPM, VTX, NLK), recorded at Suva (18.1°S,
178.5°E, L = 1.16), showed the most frequent occurrence on the
NWC signal and least on the VTX. Daytime early/fast events on
the NWC transmission are (0.2–0.5 dB) with only negative
amplitude perturbations with comparatively lower recovery
times (10–30 s) as compared with most nighttime events with
amplitude perturbations of 0.2–1.5 dB and recovery times of
20–80 s. The World-Wide Lightning Location Network
detected causative lightnings for 74 of 453 early VLF events
out of which 54 (73%) were produced due to narrow-angle
scattering, and by 20 (27%) due to wide-angle scattering (please
see Earth Planets Space, 65, 25–37, 2013). VTX signal was
analysed to investigate VLF perturbations associated with
earthquakes occurring in the Indonesian region within fifth
Fresnel zone along the TRGCP. The results of this analysis
have been published in JASTP, 102, 71–80, 2013.
We also record the ELF-VLF data using the Atmospheric
Weather Electromagnetic System for Observation Modeling
and Education (AWESOME). The analysis of short-timescale
perturbations on VLF transmitter signals recorded both with
SoftPAL and AWESOME shows one to one correlation. The
AWESOME recoding was conducted during January 213 at a
remote side in the western Fiji. The results of this campaign
will be presented in the forthcoming VERSIM workshop to be
held during 20-24 January 2014 at Otago University, Dunedin,
New Zealand. For our collaborative work with colleagues from
different organisations, please read; JGR (Space Physics), VOL.
118, 1–13, doi:10.1002/jgra.50089, 2013, Monthly Weather
Review, 141, 1358-1574, 2013, Natural Hazards and Earth
System Sciences, 13, 2331–2336, 2013, JGR (Space Physics,
118, 1–11, doi:10.1002/2013JA01908, 2013.
A GSV4004B receiver specifically designed for TEC and
ionospheric scintillation measurements was installed this year in
July. This can locate up to 11 GPS signals at two frequencies of
L1 and L2 signals (1575.42 MHz and 1227.6 MHz) and
measures phase and amplitude at 50-Hz rate and code/carrier
divergence at 1-Hz rate for each satellite being tracked. It
computes TEC from combined frequencies pseudorange and
carrier phase measurements. This system along with the
SoftPAL will provide an opportunity to study both lower (Dregion) and upper (F-region) ionosphere particularly under the
strong space weather (geomagnetic storm and solar flare)
conditions. The data recoded during 2010-2011 have been
analysed on which a students has been awarded the Master’s
degree.
The Research and International office of the University of
the South Pacific (USP) has released its electronic research
repository of the research (publications) generated during the
staff affiliation with USP. For details please visit
http://repository.usp.ac.fj/
Germany - University of Applied Sciences, Osnabrueck report
by Ernst D. Schmitter.
Exploiting continuous amplitude and phase recordings from
VLF/LF MSK transmitters again was the main topic of this
year’s activities at our mid latitude site (52°N, 8°E). These data
provide the basis for our model of solar flare induced lower
ionosphere changes. Besides looking for the effects of forcing
from above some lightning caused long recovery events (~15
minutes relaxation time) have been seen with the VLF/LF data
during a strong thunderstorm at the North Sea (4th of Nov.
3
2012). Extensive modeling of the involved EMP processes
using precise time and location data provided by the WWLLN
has been done and presented - especially at this year’s URSI
national meeting in Miltenberg, Germany, Sep. 23.-25., within
a special session on the occasion of the 100th birthday of
Professor Karl Rawer, a pioneer of ionospheric physics
research in Germany and initiator of the IRI. In the presence of
many international guests he followed the session.
Many of the current VLF/LF data plots (and a few months
back) are available at: electricterra.com/Ernst
This years publications and presentations:
Schmitter, E. D, 2013, Modeling solar flare induced lower ionosphere changes
using VLF/LF transmitter amplitude and phase observations at a midlatitude
site, Ann. Geophys., 31, 765-773, 2013
Schmitter, E.D, 2013, Characterizing lower ionosphere forcing by a strong
lightning stroke using VLF/LF radio wave remote sensing and propagation
modeling, European Planetary Science Congress 2013 (EPSC2013), P53, Sept.
8.-13.,2013, London, UK
Schmitter, E.D, 2013, VLF/LF radio wave remote sensing and propagation
modeling of lightning caused long recovery events within the lower
ionosphere, Kleinheubacher Tagung, URSI national chapter Germany,
Miltenberg, Sep. 23.-25., 2013, KHT2013-special session.3.3
Greece - University of Crete report by Christos Haldoupis.
The Ionospheric Physics Laboratory, at the Physics
Department, University of Crete continued during 2013 the
operation of an automated Stanford VLF narrow-band receiver.
The Crete VLF station is part of the AWESOME VLF network
(http://nova.stanford.edu/~vlf/awesome), which is designed to
investigate globally the Earth’s VLF environment.
In 2013, we have continued participating and supporting the
EuroSprite campaigns and the TEA-IS (Thunderstorm Effects
on the Atmosphere-Ionosphere System) European Science
Foundation project. Our research focused on lightning relating
VLF topics, among them the impulsive VLF signatures, known
as early VLF events. These are sudden nighttime VLF
perturbations associating with direct lightning effects in the D
region ionosphere, which occur in close association with
Transient Luminous Events (TLEs), mainly sprites and elves.
In 2013, we continued collaboration with colleagues from
institutions in USA, Denmark, Spain, Italy, Israel and New
Zealand. For a summary of our activities, scientific
contributions as well as paper reprints see: http://calcrete.physics.uoc.gr/VLF-sprites/VLFmain.html
The highlight of our 2013 research (published in the Journal
of Geophysical Research) is the identification of the VLF
signature of elves. This relates to a subclass of early fast events
which have rapid onsets but unusually long recoveries of many
minutes, labeled as LOREs, an acronym for LOng Recovery
Early events. We identified LORE as a distinct category of
early VLF events, whose signature may occur either on its own
or alongside the short-lived typical early VLF event. Since
LORE onsets coincide with powerful lightning strokes of either
polarity (±), we infer that they are due to long-lasting
ionization changes in the uppermost D region ionosphere
caused by electromagnetic pulses (EMP) emitted by strong
±CG lightning peak currents of typically >250 kA, which are
also known to generate elves. The LORE perturbations are
detected when the discharge is located within ~250 km from
the great circle path (GCP) of a VLF transmitter-receiver link.
The probability of occurrence increases with stroke intensity,
and approaches unity for discharges with peak currents >
~300 kA. LOREs are nighttime phenomena that occur
preferentially in winter and over the sea, when strong ±CG
discharges are more frequent and intense. The evidence
suggested that LORE as a distinct signature representing the
VLF fingerprint of elves, a fact which, although was predicted
by theory, it escaped identification in the long-going VLF
research of lightning effects in the lower ionosphere. More
research, both observational and theoretical, is presently under
way aiming to a better physical understanding of the LORE
VLF phenomena.
2013 Publications and conference presentations:
Links between mesopause temperatures and ground-based VLF narrowband
radio signals, Silber, I., C. Price, C. J. Rodger, and C. Haldoupis, J. Geophys.
Res. Atmos. 118, doi:10.1002/jgrd.50379, 2013.
The VLF fingerprint of elves: Step-like and long-recovery early VLF
perturbations caused by powerful ±CG lightning EM pulses, C. Haldoupis, M.
Cohen, E. Arnone, B. Cotts, and S Dietrich, J. Geophys. Res., Vol. 118, 1-11,
doi:10.1002/jgra.50486, 2013.
Long Lasting upper D region ionospheric modifications caused by intense +/lightning discharges, C. Haldoupis, European Geosciences Union General
Assembly, April, 07-13, Vienna, Austria, 2013.
Step-like and long recovery Early VLF perturbations caused by EM pulses
radiated by powerful ±CG lightning discharges, C. Haldoupis, International
Association of Geomagnetism and Aeronomy, 12th General Assembly, August
26-31, Merida, Mexico, 2013.
Hungary - Space Research Group, Eötvös University,
Budapest report by János Lichtenberger.
The Space Research Group of Eötvös University continued
the theoretical modeling and model-calculations of
monochromatic
and
transient
(Ultra
Wide
Band)
electromagnetic signals and the evaluation and comparison of
the results with the measured data-base recorded at terrestrial
stations and on board of satellites.
In the field of the theoretical model development of the full
wave solutions of the Mawell’s equations, further work is made
on the general solution of the electromagnetic wave propagation
in general relativistic situations
In PLASMON EUFP7-Space project, we continued the
development of the Automatic Whistler Detector and Analyzer
Network, the installation of the Automatic Whistler Analyzer
(AWA) algorithm has been installed and is under a thorough
test at Tihany. The algorithm will be installed at other nodes of
AWDANet soon. We made the first important step in the
calibration of equatorial electron densities obtained from
whistler inversion with in-situ cold plasma measurements: the
electron densities derived from upper hybrid measurements on
RBSP satellites were used to calibrate with densities from
whistlers recorded at Rothera. The preliminary results show an
excellent agreement between the data from two sources,
confirming the validity of the physical models (wave
propagation, field-aligned density distribution, equatorial
electron density distribution and magnetic field) used in the
inversion procedure.
Systematic investigation in archived DEMETER wave
recordings were continued. Compartive study of one-hop
whistlers, occurred simultaneously in ground stations, detected
automatically by the AWDANet, and identified in on-board
LEO satellite recordings, during nearby passes was performed.
Preliminary results draw the probable extent whistler
wavefronts in the topside ionosphere, and confirm the picture of
local guided propagation. New detection algorithm, optimized
for lightning generated fractional-hop whistlers, recorded onboard was developed, and applied in 6.5 years of burst wave
data.
4
The Russian-Hungarian-Ukrainian Chibis-M microsatellite,
with SAS3 ULF-VLF experiment on board has been properly
operated since its successful launch to circular LEO orbit in
February 2012. Detailed analysis of wave recordings is in
progress, including time domain waveforms and VLF
monitoring spectra, as well as in data sets of on board eventcounting routine. Recordings of the Chibis-M satellite, being
the sole ionospheric spacecraft currently performing regular
wave recordings in the topside ionosphere, represent unique
database in space weather research.
After successful delivery to the ISS in late 2012, the
OBSTANOVKA complex space experiment, including a
specific SAS3 wave analyzer instrument was installed on the
external platform of the Russian ZVEZDA module in April
2013, during a space walk of two astronauts. The experiments
started as scheduled.
India - Dept. of Electronics and Communication Engineering,
R.B.S. Engg. Technical Campus, Bichpuri, Agra, report by
Birbal Singh.
Effects of two events of X-ray bursts followed by solar
proton events (SPEs) occurred on 22 September, 2011 and 06
July, 2012 on the variation of first mode Schumann resonance
(SR) frequency monitored at a low latitude station, Agra
(Geograph. lat. 27.2°N, long. 78°E) India are examined. The
variation of average first mode SR frequency shows a sudden
increase in coincidence with the X-ray bursts and a decrease
associated with the peak flux of SPE. The increases in the
frequency in the two cases are 8.4% and 10.9% and
corresponding decreases are 4.3% and 3.3% respectively. The
increases in the frequency are interpreted in terms of growth of
ionization in the upper part of D-region ionosphere due to Xray bursts and decreases are interpreted in terms of low
ionization due to reduction in the height of the D-region
ionosphere in the polar region. The variation of SR frequency
is observed to be consistent with other observatories at middle
and high latitudes. The effect of X-ray flares are also examined
on the D-region of the ionosphere at low and equatorial
latitudes by analyzing the amplitude data of VLF transmitter
signal (NWC, f=19.8 kHz) monitored at Agra. The flare effect
observed prior to sun-set hours shows increase and decrease of
electron density in this region of the ionosphere also.
The results of solar flares induced D-region perturbation
studies along a short path (GCP = 6690 km) lying entirely in
the low and equatorial latitude region are studied and compared
with those made along similar paths at middle and high
latitudes. We use softPAL receiver and monitor NWC signal
(f=19.8 kHz) transmitted from Australia (Geograph. lat.
21.8°S, long. 114.1°E), and received at Agra (Geograph. lat.
27.2°N, long. 78°E). We find that amplitude and phase
perturbations are mostly enhancements type which show unlike
those at middle and high latitude, low magnitudes but strong
linear correlation(coefficient = 0.917) with increasing X-ray
flux intensity. Similarly, the time delays between the peaks at
the flux intensity and amplitude enhancements show a
decreasing trend with the increase in the intensity. The zenith
angle variation does not influence the data. The electron
density variation shows exponential increase with increasing
intensity and decreasing height.
Employing a dual frequency GPS-receiver, ionospheric total
electron (TEC) measurements have been in progress at Agra
station in India (Geograph. lat. 27.2°N, long. 78°E) since 1
April 2006. The TEC data have been analyzed for a period of
one month from 1 April-1 May 2013 to examine the effect of
multiple earthquakes, some of which occurred on the same day
of 16 April 2013, and others occurred in the same month of
April, 2013 in India and neighbouring countries. We process the
data using quartile and epoch analysis based statistical
techniques and show that out of all the earthquakes, the one of
the largest magnitude (M = 7.8) that occurred on Pakistan-Iran
border caused anomalous enhancements and depletions in TEC
1-9 days before the occurrence of main sock. The E×B drift
mechanism is suggested for the anomalies to occur in which the
seismogenic electric field E is generated in a process suggested
by Pulinets (2004).
India - KSK Geomagnetic Research Laboratory, Indian
Institute of Geomagnetism, Allahabad report by Rajesh Singh.
From 2007 Indian Institute of geomagnetism continues to
operate VLF stations in India at Allahabad (Geomag lat.
~16°N), Nainital (Geomag lat. ~20°N) and Varanasi (Geomag
lat. ~16°N) in collaboration with Stanford University, USA.
These stations are among the lowest latitude locations stations.
Since 2011 we also installed under collaboration with our
Hungarian colleagues from Space Research Group, Etvos
University, Hungary an Automatic Whistler Detector (AWD)
system for automatic detection of whistlers at all the three
stations. The study concentrate in particular on phenomena like
lightning discharges, radio atmospherics/tweeks, whistlers, VLF
emissions etc. and D-region ionospheric perturbations by
phenomena such as transient luminous events (TLE’s), cosmic
gamma-ray flares, terrestrial gamma ray flashes (TGF's), solar
flares, solar eclipses, geomagnetic storms, Earthquake precursor
and space weather study. During past 2-3 year we have been
concentrating on the low latitude ‘Whistlers’ with the
observation of good number of whistlers on various nights
during last 2-3 years. In our recent publications we were able to
determining the location of the causative lightning strikes
around the conjugate region of recording station in Indian
Ocean and ducted mode of propagation in low latitudes. Since
2012 we also operate two stations in India for the observation of
‘Transient Luminous Events’ (TLE’s) and were able to
recorded good number of TLE’s for the first time in Indian
subcontinent.
1. As. K. Singh, A.K. Singh, Rajesh Singh, R.P. Singh, Solar Flare induced Dregion ionospheric perturbations evaluated from VLF measurements,
Astrophysics and Space Sciences, DOI 10.1007/s10509-013-1699-4, 2013.
2. P.R. Srivastava, Sneha A. Gokani, Ajeet K. Maurya, Rajesh Singh, Sushil
Kumar, B. Veenadhari, R. Selvakumaran, A.K. Singh, D. Siingh, J.
Lichtenberger, One-to-one relationship between low latitude whistlers and
conjugate source lightning discharges and their propagation characteristics,
Advances in Space Research, http://dx.doi.org/10.1016/j.asr.2012.07.005, 2013.
3. S. Sripathi, N. Balachandran, B. Veenadhari, Rajesh Singh and K.
Emperumal, Response of the equatorial and low-latitude ionosphere to an
intense X-class solar flare (X7/2B) as observed on 09 August 2011, Journal of
Geophysical Research, doi: 10.1002/jgra.50267, 2013.
4. A. K. Maurya, Rajesh Singh, B. Veenadhari, S. Kumar, and A. K. Singh Subionospheric very low frequency perturbations associated with the 12 May 2008
M = 7.9 Wenchuan earthquake, Natural Hazard and Earth System Sciences,
doi:10.5194/nhess-13-1-2013.
5. B. Veenadhari, R. Selvakumaran, Rajesh Singh, Ajeet K. Maurya, N.
Gopalswamy, Sushil Kumar, T. Kikuchi, Coronal mass ejections-diven shocks
and the associated sudden commencements/sudden impulses, Journal of
Geophysical Research, doi:10.1029/2011JA017216, 2012.
6. B. Veenadhari, Sandeep Kumar, S. Tulasi Ram, Rajesh Singh, S. Alex,
Corotating interaction region (CIR) induced magnetic storms during solar
minimum and their effects on low-latitude geomagnetic field and ionosphere,
Indian Journal of Radio & Space Physics, 41, 306-315, 2012.
5
7. Ashutosh K. Singh, Rajesh Singh, B. Veenadhari, A.K. Singh, Response of
low latitude D-region ionosphere to the total solar eclipse of 22 July 2009
deduced from ELF/VLF analysis, Advances in Space Research,
http://dx.doi.org/10.1016/j.asr.2012.07.005, 2012.
India - Department of Physics, University of Lucknow,
Lucknow, report by Ashok K. Singh.
University of Lucknow, Lucknow (India) is a premier
institution of higher education in Northern part of the country.
Department of Physics is associated with many research
activities including those in the field of Atmospheric and Space
Sciences. Since December 2010, recording and analysis of
whistlers and VLF emissions at lower latitude station Lucknow
(Geomag. Lat., 17.60°N, Geomag. Long., 154.50°E) is
continued in order to observe and detects whistlers and VLF
emissions for estimation of various medium parameters. The
VLF antenna at Lucknow is made up of two perpendicular
magnetic loops, oriented N-S and E-W. This antenna will be
part of AWDAnet, the Automatic Whistler Detector and
Analyzer system's network. Using this VLF receiver, we have
observed more than 300 tweeks of third or higher harmonics.
Analysis provides electron density and reflection height of the
D-region ionosphere. Fig. 1 shows a typical example of third
harmonic tweeks recorded at our station.
Fig. 1: A typical example of third harmonic tweeks recorded at Lucknow
In relation to this work, we have also started to work with
the amplitude and phase measurements of fixed frequency VLF
signals transmitted from ground based transmitters which are
used in the study of the D-region perturbation phenomena. We
are also involved in the study of solar flares, geomagnetic
storms and their interpretation related with space weather
phenomena.
Japan - Chiba University, Chiba, report by Hiroyo Ohya.
We have conducted Asia VLF observation network
(AVON) in South-East Asia: Tainan (Taiwan), Saraburi
(Thailand), Pontianak (Indonesia), Los Baños (Philippines)
since 2007 (Figure 1). We have a plan of a new observation
system in Vietnamese construction in December, 2013. The
aim of the AVON is to investigate the D- and lower E-region
ionosphere, lightning, and coupling between lightning and the
lower ionosphere in South-East Asia [Adachi et al., 2008a].
Fourteen universities/institutes participate in AVON: Hokkaido
University (Prof. Yukihiro Takahashi), Tohoku University (Dr.
Fuminori Tsuchiya), Salesian Polytechnic (Dr. Kozo
Yamashita), Nagoya University (Prof. Kazuo Shiokawa and
Dr. Yoshizumi Miyoshi), JAMSTEC (Drs. Hisayuki Kubota
and Miki Hattori), Tokyo Metropolitan University (Prof. Jun
Matsumoto), National Cheng Kung University (Taiwan, Dr.
Alfred B. Chen), Chularongkorn University (Thailand, Miss.
Boossarasiri Thana), LAPAN (Indonesia, Mr. Timbul Manik),
PAGASA (Philippines, Dr. Esperanza Cayanan), University of
the Philippines (Philippines), AMO (Vietnam, Dr. Hoang Gia
Hiep), Hanoi University of Science (Vietnam, Dr. Thanh NGODUC), and Chiba University (Drs. Hiroyuki Nakata and Hiroyo
Ohya).
correspond to a height increase of 5–6 km for the paths across
the eclipse and 1–2 km for partial eclipse paths.
We are preparing that quick-look files of the AVON magnetic
component data can be used on Inter-university Upper
atmosphere Global Observation NETwork (IUGONET).
http://www.iugonet.org/en/index.html
1. Adachi et al., Monitoring of Lightning Activity in Southeast Asia: Scientific
Objectives and Strategies, Kyoto Working Papers on Area Studies: G-COE
Series, 11, 1-20, 2008a.
2. Adachi et al., Electric fields and electron energies in sprites and temporal
evolutions of lightning charge moment, J. Phys. D: Appl. Phys., 41, 234010,
2008b.
3. Ohya et al., Reflection height of daytime tweek atmospherics during the
solar eclipse of 22 July 2009, J. Geophys. Res., 117, A11310,
doi:10.1029/2012JA018151, 2012.
New Zealand - University of Otago, Dunedin, report by Craig
J. Rodger.
Figure 1. Observation sites of AVON. The color indicates total lightning flash
counts by LIS/TRMM satellite in 1998-2011.
Using two orthogonal loop antennas, a monopole antenna,
and a dipole antenna, electromagnetic waves originated from
lightning and transmitters in the frequency range of 0.1–70 kHz
are measured at each site. At each site, a set of orthogonal loop
antennas is used to observe the horizontal magnetic field
components of north–south (N-S) and east–west (E-W)
directions induced by lightning discharges. A set of dipole and
monopole antennas is also used to observe the vertical electric
field of electromagnetic waves radiated by lightning and
artificial transmitters. Signals are amplified by a pre-amplifier
and a main amplifier and then recorded by three PCs together
with the GPS time code signals. The first PC (PC1) is used for
monitoring lightening, and the second (PC2) and third (PC3)
PCs are used for monitoring the lower ionosphere. PC1
regularly records the waveforms of lightning atmospherics in
both the electric and magnetic field components. The sampling
frequency is 100 kHz. The obtained data allow us to detect the
occurrence location and the timing of source lightning with
accuracies of 10 km and 10 μs. Furthermore, because the
system detects atmospherics in a wide frequency range of 1–
70 kHz, it is possible to derive the current moment change of
lightning, which is an important parameter in the production of
transient luminous events (TLEs) such as sprites, elves, and
blue/gigantic jets [Adachi et al., 2008b]. PC2 records the
waveforms of two-component (N-S and E-W) magnetic-field
data of tweeks for 2 minutes every 10 minutes. The measured
frequency range is up to 10 kHz, with a sampling frequency of
20 kHz. PC3 records the vertical electric field of radio waves
emitted from artificial transmitters with a sampling frequency
of 200 kHz. By processing the real-time data, PC3 records the
power and phase of the pre-set transmitter signals at a rate of 10
Hz. The obtained data are used for monitoring the D- and lower
E-region ionosphere.
We have reported D-region response during a total solar
eclipse of 22 July, 2009 using AVON data [Ohya et al., 2012].
In the paper, we reported that 16 tweek atmospherics were
observed during the daytime solar eclipse at Moshiri, Japan,
where the magnitudes of the solar eclipse were low to be 0.458.
The average change in the phase delay of the LF transmitter
signals was 109 degrees for the paths that crossed the eclipse
path and 27 degrees for the paths that did not cross the eclipse
path. Assuming a normal daytime height for LF waves of 65
km, a ray tracing analysis indicates that the variations in phase
6
We continue to operate the following experimental
measurements locally in Dunedin: 1) the VLF Doppler
Experiment which monitors whistler-mode signals from VLF
transmitters that have propagated through the plasmasphere,
predominantly inside whistler ducts. 2) several narrowband
receivers (OmniPAL, AbsPAL, SoftPAL and Ultra MSK)
which log changes in the phase and amplitude of powerful VLF
communications transmitters (~16-30 kHz) to study
subionospheric propagation. 3) an Automatic Whistler Detector
and Analysis (AWDA) receiver operating in collaboration with
Eötvös University. 4) a receiver and central processing
computer of the World Wide Lightning Location Network
(WWLLN). We also operate UltraMSK narrow-band loggers in
Antarctica (near Scott Base, with support from Antarctica New
Zealand), and Ministik Lake (near Edmonton, Canada, with
support from the University of Alberta). Narrow-band
observations are also being made using some WWLLN
receiver locations, testing new software capability. We play a
core role of the AARDDVARK global network of
subionospheric VLF monitors and also the real-time to the
WWLLN lightning consortia.
We have visited both of our distant field sites. James
Brundell and Craig Rodger visited the Ministik Lake VLF
receiver in July 2013, and found it in good condition. In
November 2013 James and Otago PhD student travelled to
Scott Base to work on our receiver there. They found the
weather conditions quite harsh (and cold)! In 2013 the group
send 3 members to the IAGA conference in Merida, Mexico
(Craig, PostDoc Ian Whittaker and PhD student Aaron
Hendry), and also to the CAWSES-II International Symposium
in Nagoya, Japan (Craig, and MSc students Kathy CresswellMoorcock and Jason Neal). This year all the younger members
of the Otago research group have had research papers
published, which I have listed at the end of our report.
This year Neil Thomson travelled to Alaska, Norway and
Germany to make measurements of the powerful VLF
transmitters. These campaigns are focused on understanding
the typical electron number density profiles of the D-region,
and particularly to determine the profiles suitable to describe
subionospheric VLF propagation.
In 2013 Craig Rodger has again been mostly focused on the
detection and effects of energetic electron precipitation from
the radiation belts, and in particular trying to understand the
impact of precipitation on the upper atmosphere and its
coupling to Earth's climate. Through our collaborators we have
been trying to expand our space-physics activities to examine
the atmospheric changes caused by precipitation as well as
coupling to polar climate. This has been a very successful year
for our group, with a high output. Craig recognises that his
PostDoc, research students, and international collabotrators
have had a big role in this output. We continue to enjoy
working with the wider world, from our far-flung location in the
South Pacific. An up to date listing of our publications is
available from the Space Physics Group's website:
http://www.physics.otago.ac.nz/nx/space/space-physics-publications.html.
This includes PDFs of our published work, where-ever possible.
1. Rodger, C J, A J Kavanagh, M A Clilverd, and S Marple, Comparison
between POES energetic electron precipitation observations and riometer
absorptions: Implications for determining true precipitation fluxes, J. Geophys.
Res., doi:10.1002/2013JA019439, 2013.
2. Newnham, D A, P J Espy, M A Clilverd, C J Rodger, A Seppälä, D J
Maxfield, P Hartogh, K Holmén, and R B Horne, Observations of nitric oxide
in the Antarctic middle atmosphere during recurrent geomagnetic storms, J.
Geophys. Res., doi:10.1002/2013JA019056, 2013.
3. Whittaker, I C, R J Gamble, C J Rodger, M A Clilverd and J A Sauvaud,
Determining the spectra of radiation belt electron losses: Fitting DEMETER
IDP observations for typical and storm-times, J. Geophys. Res.,
doi:10.1002/2013JA019228, 2013.
4. Clilverd, M A, N Cobbett, C J Rodger, J B Brundell, M Denton, D Hartley, J
Rodriguez, D Danskin, T Raita, and E L Spanswick, Energetic electron
precipitation characteristics observed from Antarctica during a flux dropout
event, J. Geophys. Res., 118, doi:10.1002/2013JA019067, 2013.
5. Cresswell-Moorcock, K, C J Rodger, A Kero, A B Collier, M A Clilverd, I
Häggström, and T Pitkänen, A reexamination of latitudinal limits of substormproduced energetic electron precipitation, J. Geophys. Res., 118,
doi:10.1002/jgra.50598, 2013.
6. Verronen, P T, M Andersson, C J Rodger, M A Clilverd, S Wang, and E
Turunen, Comparison of modeled and observed effects of radiation belt electron
precipitation on mesospheric hydroxyl and ozone, J. Geophys. Res., 118,
doi:10.1002/jgrd.50845, 2013.
7. Neal, J J, C J Rodger, and J C Green, Empirical determination of solar proton
access to the atmosphere: impact on polar flight paths, Space Weather, 11, 420433, doi:10.1002/swe.20066, 2013.
8. Lichtenberger, J, M A Clilverd, B Heilig, M Vellante, J Manninen, C J
Rodger, A B Collier, A M Jorgensen, J Reda, R H Holzworth, R Friedel, and M
Simon- Wedlund, The plasmasphere during a space weather event: First results
from the PLASMON, J. Space Weather Space Climate,3 (A3),
http://dx.doi.org/10.1051/swsc/2013045, 2013.
9. Silber, I, C Price, C J Rodger, and C Haldoupis, Links between mesopause
temperatures and ground-based VLF narrowband radio signals, J. Geophys.
Res., 118, doi:10.1002/jgrd.50379, 2013.
10. Seppälä, A, H Lu, M A Clilverd, and C J Rodger, Geomagnetic activity
signatures in wintertime stratosphere-troposphere temperature, wind, and wave
response, J. Geophys. Res., 118, doi:10.1002/jgrd.50236, 2013.
11. Carson, B R, C J Rodger, and M A Clilverd, POES Satellite Observations of
EMIC-wave driven Relativistic Electron Precipitation during 1998-2010, J.
Geophys. Res., 118, 1–12, doi:10.1029/2012JA017998, 2013.
12. Hendry, A T, C J Rodger, M A Clilverd, N R Thomson, S K Morley, T
Raita, Rapid radiation belt losses occurring during high speed solar wind stream
driven storms: importance of energetic electron precipitation, in Dynamics of
the Earth's Radiation Belts and Inner Magnetosphere, Geophys. Monogr. Ser.,
vol. 199, edited by D. Summers et al., 213–223, AGU, Washington, D. C.,
doi:10.1029/2012GM001299, 2013.
Russia - Space Research Institute of RAS (IKI), Moscow,
report by Ilya Kuzichev, David Shklyar, Elena Titova, and
Dmitry Vavilov
The work on the problem of lower hybrid resonance (LHR)
reflection of whistler-mode waves has been continued. For
some ionospheric parameters, especially for those which are
typical of daytime ionosphere, LHR reflection can take place in
the F-layer of the ionosphere, at the heights of about 300 km. In
this region, collision frequencies (mostly, electron to ion) are
7
high enough, and the collisional damping of the wave should
be taken into account. Hence, geometrical optics approach to
the description of LHR reflection is not valid in the vicinity of
reflection point, and we have developed a full-wave approach
to the problem. With this method, the reflection coefficient as a
function of wave frequency has been calculated. Wave
absorption in the reflection region decreases the reflection
coefficient so that it becomes less than unity. Interestingly, the
reflection coefficient shows a non-monotonic behavior as a
function of wave frequency. Such behavior is most evident in
the night-time ionosphere (more precisely, for ionospheric
plasma parameters typical of 10 pm local time, mid-latitude
ionosphere), when two local maxima of LHR frequency are
formed, with the global maximum in the F-region. Since the
reflection coefficients play significant role in the theory of
whistler-mode cyclotron maser, these results might be
important not only for analyzing wave phenomena, but for selfconsistent modeling of magnetosphere’s dynamics. Also the
strong collisional damping of the quasi-electrostatic whistlermode wave in the F-region of the day-time ionosphere has been
shown. It substantially reduces the efficiency of scattering of
such waves from F-region irregularities into the transmission
cone. This result is consistent with the fact that VLF waves are
observed at the ground far more often at night than during the
day.
Kuzichev I. V., D. R. Shklyar, Full-wave description of the lower hybrid
reflection of whistler waves, Plasma Physics Reports, V.39, Is. 10, pp. 795808, 2013
Kuzichev, Ilya; Shklyar, David, On the full-wave approach to the problem of
lower hybrid reflection of whistler-mode waves in the ionosphere, IAGA 12th
Scientific Assembly, 26-31 August, 2013
The problem of resonant wave-particle interaction between
oblique whistler-mode waves generated by VLF transmitter
and relativistic electrons populating the outer radiation belt has
been investigated, with the main focus on particle capturing
into resonance. In the case of monochromatic waves, when the
well-known integral of motion exists, it is possible to express
the resonant particle parallel momentum through this integral
of motion and particle coordinate along the field line on which
is the particle trajectory is centered. The topology of the
resonant surface depending on the integral of motion has been
studied. In general, for a given point along the field line, there
are two roots for resonant parallel momentum: positive and
negative. At some points these roots can merge into zero,
giving rise to the so called relativistic turning acceleration
discovered by Y. Omura for the case of longitudinal
propagation. The main result of the study is the following: we
found that for the case of interaction with oblique waves, the
effective amplitude of interaction becomes essentially
asymmetric with respect to the direction of the resonant
particle motion, i.e. towards the geomagnetic equator and away
from it. The consequences are twofold: on the one hand, this
effect increases the efficiency of acceleration of trapped
particles that cross the equator because the particles become
detrapped soon after they crossed the equator due to
oscillations of the effective amplitude. On the other hand, the
same behavior of the effective amplitude holds for the particles
which have a turning point before the equator: once the particle
has turned, the effective amplitude starts to oscillate and
particle becomes detrapped. This decreases the efficiency of
relativistic turning acceleration as compared to the case of
longitudinal propagation.
Kuzichev, Ilya; Shklyar, David, Resonant interaction of relativistic electrons
with an oblique monochromatic whistler-mode wave, IAGA 12th Scientific
Assembly, 26-31 August, 2013
Using the measurements from the DEMETER satellite for 3
years we have calculated the maps of the lower hybrid
resonance (LHR) frequency over the globe, and the maps of
VLF spectral intensity at the frequencies of Alpha navigation
transmitters. These maps demonstrate a significant dependence
of the spectral intensity in the transmitter conjugate region on
the relation between the signal frequency and the LHR
frequency above the observation point. Variations of plasma
distribution and/or wave spectral features in the ionosphere
were suggested by many authors as possible earthquake
precursors, and the change of plasma density and temperature
above seismic regions were reported in the literature. These
quantities are known to influence the LHR frequency profiles in
the upper ionosphere and the magnetosphere, which, in turn,
strongly affects the propagation of quasi-resonance VLF waves
with frequencies close to the maximum of the LHR frequency
on the propagation path. This makes the VLF signals a tool of
registration of ionospheric perturbations. Then, using the
DEMETER data and the earthquake database from the US
geological survey server we have performed a statistical
analysis of the LHR frequency over seismic regions and found
an appreciably different behavior of the LHR frequency before
earthquakes, as compared to its regular behavior, for several
seismic regions. Although this difference is statistically
significant, in each particular case the ionospheric perturbations
may be related to different processes in the Earth's atmosphere,
ionosphere, and the magnetosphere, other than gathering
earthquakes. Thus, the unexpected variations in the LHR
frequency profile, revealed from the variations of VLF
transmitter signals, should only be considered as one indicator
in a list of possible earthquake precursors.
Vavilov, D. I., D. R. Shklyar, E. E. Titova, M. Parrot, Study of the lower hybrid
resonance frequency over the regions of gathering earthquakes using
DEMETER data, J. Atm. Sol.-Terr. Phys., V. 100, p. 1-12
Russia - Yu.G. Shafer Institute of Cosmophysical Research and
Aeronomy SB of RAS, Yakutsk, report by Victor Mullayarov
The study of the effects of neutron observations using the
standard neutron monitor during periods of the nearest lightning
strikes have been continued. The sessions of fast registration
(with microsecond resolution) of the neutron intensity during
thunderstorm activity have been carried out. The results allow
to make a conclusion on the exclusion of electromagnetic
lightning interference as a possible reason of impulses recorded
with the neutron monitor during periods of nearest lightning
strikes.
We continue participating in the World Wide Lightning
Location Network (WWLLN). The data of WWLLN are used,
in particular, in the study of seismic effects in the lower
ionosphere by data of the monitoring of electromagnetic
lightning signals - atmospherics, passing over the earthquake's
epicenters. Previously it has been found that the effects of
earthquakes and their possible precursors in the form of
increasing the average amplitude of atmospherics are registered
for the strong (magnitude >5), not deep (depth <50 km)
earthquakes. However, considering the case of strong (M = 8.2)
earthquake on May 24, 2013, which has occurred not far from
the Kamchatka Peninsula at a depth of over 600 km, we can see
that the some strong deep-focus earthquakes can also cause
disturbances in the lower ionosphere.
8
Slovenia/Serbia joint report - University of Nova Gorica
(Slovenia) and Institute of Physics, Belgrade (Serbia) report by
V. Žigman (UNG) and D. Šulić (IPB).
We have continued the monitoring of the VLF signals on
short and long paths to Belgrade, namely from transmitters
GQD, DHO, ICV and NAA, NWC respectively, mainly
analyzing solar X-ray flares and the induced electron density
enhancements.
The study of VLF data from the Antarctica stations Scott
Base and Casey has been extended thanks to the active and
helpful cooperation of Craig Rodger, Otago University, and
Mark Clilverd, British Antarctic Survey. Through this
collaboration we have been able to 'observe' flares occurring at
nighttime UT, which have been frequent in the last flary period
of October 2013. We have used these data in deducing
enhancements of electron density at the upper ceiling of the Dregion , ~90 km in height, relating the deviation of amplitude
and phase of the VLF signal to the flare irradiance in the
wavelength range of EUV and soft X rays as mesured by the
LYRA radiometer on board of Proba2. A short progress report
was presented during the ESWW10 (Brussels, 18-22
November 2013).
We have shown the outstanding efficiency of the VLF
monitoring of solar proton events, by studying the Ground
Level Enhancement event of December 13, 2006 (GLE70). The
data on the NAA/24.0 kHz – Belgrade path have been used in
parallel with the neutron monitor data as recorded by the
neutron monitor network nmdb.eu. It has been shown that the
VLF technique not only detects solar proton events but also
reproduces the time structure of the event in remarkable
agreement with the neutron monitor findings. In collaboration
with the Department of Space Science of the Institute of
Experimental Physics in Košice the results have been presented
at the ESWW10 and a paper has been submitted to Advances
in Space Research.
Taiwan - National Cheng Kung University, Tainan, report by
Kaiti Wang.
Two papers related to observed emissions of ELF-signals at
Lulin station and correlations with seismic activities are
published this year.
1. Ho, S. M., K. Wang, A. B. C. Chen, H. T. Su, S. M. Huang, R. R. Hsu, T. S.
Hsu (2013), Characteristics of magnetic signals observed at Lulin ELF station
and their association with earthquakes in Taiwan, Terr. Atmos. Ocean.Sci, 24,
No.2.
2. Liu, J. Y., K. Wang, C. H. Chen, W. H. Yang, Y. H. Yen, Y. I. Chen, K.
Hatorri, H. T. Su, R. R. Hsu, and C. H. Chang (2013), A statistical study on
ELF-whistlers/emissions and M≥5.0 earthquakes in Taiwan, J. Geophys. Res.,
118, 3760–3768, doi:10.1002/jgra.50356.
United Kingdom - British Antarctic Survey, Cambridge,
report by Mark Clilverd.
BROADBAND RECORDINGS in Antarctica:
Whistler-detection and data collection has continued at
Halley (L=4.5) and Rothera (L=2.9) throughout 2013 using the
Hungarian Automatic Whistler Detection (AWD) system. BAS
also continues to operate a third AWD site, at Eskdalemuir in
Southern Scotland (L=2.7). These sites operate as part of the
PLASMON FP7 project.
The Stanford University AWESOME receiver has also
operated at Rothera throughout 2013, logging broadband and
narrow-band data. The instrument is planned to return to BAS
Cambridge for overhaul at the end of 2013.
VELOX RECORDINGS at Halley, Antarctica:
Continuous (since 1992) recordings of VLF activity in 10
ELF/VLF bands, at 1-s resolution (VELOX and VELOXNET)
have been maintained at Halley in 2013. Some difficulties have
been encountered with the aerial signal quality in 2013 as a
result of wind damage, so VELOX data quality has been poor at
times.
NARROW-BAND RECORDINGS:
‘Ultra’ narrow-band recordings have continued at Halley and
Rothera (Antarctica), the Australian Casey station (Antarctica),
Forks, Seattle (USA), Sodankyla (Finland), Ottawa, St Johns,
and Churchill (all Canada), Eskdalemuir (Scotland), and Ny
Alesund (Svalbard) throughout 2013. Basic data collection at all
sites is undertaken with 0.1-1 s resolution. A limited amount of
‘Ultra’ data has been collected at a newly installed site in
Reykjavik (Iceland) during 2013 (May-September). The status
of the instrument is currently unknown.
The software VLF Doppler system has continued at Rothera
station, Antarctica (L=2.8) in 2013, receiving whistler mode
and sub-ionospheric signals primarily from NAA (24.0 kHz). A
similar Doppler system has been in operation at Marion Island,
South Africa (L=2.9) during 2013, hosted by the University of
Natal, Durban.
WWLLN sites:
British Antarctic Survey has operated three World Wide
Lightning Location Network systems in 2013. Rothera and
Halley have successfully provided lighting location information
all year. Ascension has become operational again in March
2013, after a fault throughout most of 2012.
United Kingdom - VERRI, Derbyshire, report by Andy Smith.
The VELOX instrument at Halley Antarctica, which records
radio waves in 8 bands from 500 Hz to 10 kHz with a once per
second sampling rate, began operating in January 1992 and has
continued to the present. Thus there is now an almost
uninterrupted two solar cycle long VLF/ELF data set. The most
important statistical results from the first 16 years of operation
(1992-2007), have been published (J. Atmos. Solar-Terr. Phys. 72 463475, doi:10.1016/j.jastp.2009.12.018). We are now working with
colleagues at British Antarctic Survey to extend this analysis to
the present time, and to quantify some technical issues
associated with the move of the receiver from Halley V to the
new Halley VI site. A report will be given at the forthcoming
VERSIM workshop in New Zealand.
Ukraine - Dept. of Remote Sensing, Usikov Institute for RadioPhysics and Electronics, Nat. Acad. of Sci. of the Ukraine,
Kharkov, Ukraine, report by A. Nickolaenko.
The main attention of Kharkov group was concentrated at
the following issues.
Extended treatment was developed in modeling the impact
on ELF radio propagation of the ionosphere disturbance
positioned above a future earthquake. The result was published
in the following paper:
Nickolaenko A.P. and M. Hayakawa, Localized ionospheric disturbance
over the earthquake epicentre and modifications of Schumann resonance
electromagnetic fields, Geomatics, Natural Hazards and Risk, (2013), DOI:
10.1080/19475705. http://dx.doi.org/10.1080/19475705.2013.809557
9
The improved method was developed for estimating the
effective ionospheric height and the propagation distance of the
tweek-atmospherics. It implies compensation of the waveguide
dispersion in the tweek-signal. This improves the accuracy of
deducing the cutoff frequencies, especially in the presence of
noise. Modeling was performed of the multimode tweekatmospherics in the Earth-ionosphere waveguide with the
exponential conductivity profile. We showed that accuracy of
estimating the effective waveguide height reaches the 100-400
m level for the first and higher order tweek modes. This allows
estimating the parameters of conductivity profile in a wider
range of source distances: from a few hundred to a few
thousand kilometers. Preliminary analysis of experimental
records showed a decrease of the effective height with the
increase of the mode number. The scale height of the
conductivity profile was estimated by 0.4 – 2.5 km.
A.V.Shvets, T.M. Serdiuk, Y.V. Gorishnyaya,Y.Hobara3, and M.
Hayakawa, Estimating the Lower Ionosphere Height and Lightning Location
Using Multimode "Tweek" Atmospherics, Journal of Atmospheric and SolarTerrestrial Physics. Accepted manuscript (unedited version) available online:
28-NOV-2013. DOI information: 10.1016/j.jastp.2013.11.007
We compared spectra and the waveforms of computed Qbursts for a set of realistic ELF propagation models. Emphasize
was made on the impact of a typical Schumann resonance
receiver on the waveform. Such a receiver modifies the
waveform, so that some problems might appear when
identifying the source polarity. Shifted positions of the subpeaks in the waveform might impede the correct source
distance evaluation. Compensation of the phase distortions
substantially improves the quality of the record. The paper in
Russian will be published by Radiofizika, Nizhnii Novgorod.
The new book on the Schumann resonance studies was
prepared: A. Nickolaenko and M. Hayakawa, “Schumann
Resonance for Tyros”. The book will be published by Springer,
details
can
be
found
on
their
website
(http://www.springer.com/earth+sciences+and+geography/geophysics/book/97
8-4-431-54357-2).
USA - University of Stanford, report by Morris Cohen.
A new VERSIM group is now established at Georgia
Institute of Technology (Georgia Tech), in the School of
Electrical and Computer Engineering, and will be led by
Morris Cohen, previously of Stanford University. The group
will focus on VLF remote sensing of lightning, using global
VLF receivers, NLDN/GLD360, and will continue
collaboration with Stanford. The group will also build on
previous experimental results on transionospheric propagation
of VLF signals. The group is brand new, and thus welcomes
new collaborations and opportunities.
We'd like to briefly describe four sets of results from the
past year:
(1) During the March 2011 M9.0 earthquake in Japan, we
very fortuitously had a VLF receiver about 100 km from the
epicenter, in about the closest possible place on land.
Amazingly, the receiver operated prior to, and even 2 minutes
during, the earthquake. We analyzed the data, and found
remarkable and bizarre VLF signatures, as the power lines
crumbled, rocks were stressed, and buildings shook. There's
no way to really explain these observations or link them
directly to their source, but there were very intense emissions
in the few kHz range that corresponded to the arrival of the
slow wave of the earthquake. We also searched for
electromagnetic precursors in both the broadband and
narrowband data, and found none, despite the extremely
fortuitous placement of the receiver near this extraordinarily
rare earthquake. Full results are available in this GRL paper:
http://onlinelibrary.wiley.com/doi/10.1029/2012GL052123/abstract
(2) We participated in three studies connecting the properties
of early/fast events, including recovery time, size, and
amplitude, to the properties of the lightning stroke, including
peak current and polarity. These results came out of Stanford's
AWESOME receiver network, and cover both European and
North American Early/fast events. The full results can be found
in
these
three
papers:
http://onlinelibrary.wiley.com/doi/10.1002/jgra.50448/abstract,
http://onlinelibrary.wiley.com/doi/10.1002/jgra.50489/abstract,
http://onlinelibrary.wiley.com/doi/10.1002/2013JA019087/abstract
(3) Stanford VLF receivers embedded in Vaisala's GLD360
network uncovered remarkable evidence that oceanic lightning
unleashes, on average, particularly intense lightning. Because of
GLD360's high detection efficiency (60% or higher), the
distribution of peak currents for both land and oceanic lightning
could be directly measured. The VLF radiation intensity allows
GLD360 to quantify each event with reference to NLDN peak
currents, with 6% error. Oceanic lightning was shown to be 65121% stronger on average. Although the oceans see about 10
times less lightning than land, the majority of the Earth's >75
kA strokes actually occur over the ocean. Experiments are now
underway to explain the physical reasons for this observation.
Full
results
are
available
in
this
paper:
http://onlinelibrary.wiley.com/doi/10.1002/jgrd.50508/abstract.
(4) Putting a bowtie on years of experiments, we've
compiled nearly 100 days of ELF/VLF generation with HAARP
HF heating, and put all the data into a massive database, with
millions of individual observations. We observe the diurnal
dependence of ELF/VLF generation with HF heating, noted a
"startup effect" when the heater is turned on, which may be
evidence of electron density changes, and also used theoretical
modeling to infer the radiated ELF/VLF power generated by
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HAARP, statistically. Full results can be seen in this paper:
http://onlinelibrary.wiley.com/doi/10.1002/jgra.50558/abstract
We send our regards to all our colleagues and look forward
to future discussions and collaborations.
USA - University of California, Los Angeles, report by
Richard M. Thorne and Jacob Bortnik.
The past year has been particularly busy for the UCLA
group in light of the recently launched Van Allen Probes
mission. We have published well over 20 journal papers at the
time of this writing, dealing with topics that are generally
focused on the dynamics of the Earth's radiation belts, and the
numerous waves that control these dynamics. These include: a
detailed explanation of the hiss-driven decay of the
ultrarelativistic "storage ring" discovered in 2012 by Baker et
al., a new technique to infer the spatiotemporal distribution of
chorus waves throughout the whole inner magnetosphere, new
evidence of chorus being the source of plasmaspheric hiss, a
detailed analysis of the dayside auroral precipitation by
measured chorus, a quantitative analysis of the excitation of
equatorial magnetosonic waves by measured ion ring
distributions, a model for the structure and distribution of the
chorus wave normal evolution as function of latitude and a
related observational study, and an experimental analysis of
EMIC waves based on satellite data, together with numerical
modeling of the excitation of these waves. A final study which
deserves mention, due to be published in the journal Nature
over the Christmas period, explains the unique formation of the
belt of ultrarelativistic electrons during the Oct 9, 2012
geomagnetic storm, which persisted over a period of a few
months thereafter. We will be glad to provide more information
and copies of any of the above studies to interested parties
upon request.
Merry Christmas and Happy New Year!
János Lichtenberger and Csaba Ferencz (Eötvös University, Hungary) in the mission control center of the International
Space Station at Korolev (near Moscow, Russia) on 26 April 2013, when the OBSTANOVKA experiment was installed
during a space walk by two Russian astronauts on the outer surface of the Russian ZVEZDA module.
Jacob Bortnik (UCLA, USA) taking a weekend getaway to the Hamptons, playground of the rich and famous (although the
plebs only get to play off-season!). New York, USA
Dr. Craig Rodger (Otago University, New Zealand) beside the "Governor's Palace" in the ruined Mayan city of Uxmal, on
the Yucatan Peninsula. This city is believed to have once had 15-25 thousand people living in it, but is now surrounded by
jungle and visited by tourists. Craig was in Mexico to attend the 12th IAGA Scientific Assembly in Merida, Mexico [28
August 2013].
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